The present invention relates to an indexing turret assembly for a machine tool and more particularly, to an indexing turret assembly having provisions for mounting both stationary and live tooling.
Indexing turret assemblies have found widespread use in the machine tooling industry. Such assemblies are capable of selectively positioning a plurality of diverse tools into proper alignment with a workpiece so as to allow sequential machining operations to be performed thereon.
The most common types of indexing turret assemblies are those which support tools suitable for turning operations wherein the tools are stationary with respect to a revolving workpiece or those which support tools suitable for milling, drilling, tapping, etc., wherein the tools are rotatably driven with respect to a non-rotating workpiece.
There are also indexing turret assemblies capable of supporting combinations of stationary and live tooling. Such indexing turret assemblies serve to increase the overall flexibility of the machine tool by allowing greater diversity in the machining operations.
One such machine tool is disclosed by Kolblin in U.S. Pat. No. 4,429,443. Kolblin discloses the use of an indexing turret assembly for supporting stationary as well as live tooling and includes a live tooling engagement device movable between a decoupled position and a coupled position by means of a piston and cylinder arrangement. One shortcoming associated with the Kolblin apparatus is that the live tooling drive units are separate from the indexing drive units, thus adding to the overall complexity of the turret assembly.
Smith, U.S. Pat. No. 4,656,708, owned by the same assignee as the present invention, discloses the use of an indexing turret assembly utilizing a single drive motor to provide angular rotation of the turret plate for indexing, as well as for providing the drive to the live tooling mounted on the turret. Hydraulic pressure is used to disengage the turret plate and allow the turret plate to rotate with respect to the rest of the turret. A pneumatic clutch can then be engaged to rotate the turret plate with the single drive motor until the desired tool is indexed. The turret plate is then reengaged with the turret and the clutch disengaged to allow the single drive motor to drive the live tooling.
Link, U.S. Pat. No. 5,490,307, also discloses an indexing turret assembly utilizing a single drive motor for both indexing the turret and driving the live tooling. As with Smith, hydraulic pressure is used to disengage the turret plate and allow the turret plate to rotate with respect to the rest of the turret. The single drive motor is then used to rotate the turret plate until the desired tool is indexed. However, when the turret plate is reengaged with the turret, the drive to the turret plate automatically disengages so that the single drive motor can then be used to drive the live tooling.
Hafla, U.S. Pat. No. 4,847,960 also discloses an indexing turret assembly utilizing a single drive motor for both indexing the turret and driving the live tooling. Hafla does not disengage the turret plate from the turret to index the desired tool, but uses a disengageable planetary gear arranged with the live tool bevel drive gear to index the turret.
In Smith, Link and Hafla, the single live tool bevel drive gear is always engaged with all live tooling installed in the turret plate. Thus, where more than one live tool is installed in the turret plate, all live tools installed in the turret plate will be driven when any live tool is driven. There is a substantial loss of power in driving all live tools simultaneously when it is necessary to drive only the live tool indexed to perform an operation on a workpiece. This can require a higher capacity drive unit than would otherwise be required if only one live tool is driven at a single time or can result in insufficient power being available to properly drive the live tool performing an operation. None of Smith, Link or Hafla allows the selective driving of any single one of a plurality of live tools installed at a given time.
The present invention provides a turret assembly including a rotatable indexable turret tooling plate having mounted thereon stationary as well as live tooling and wherein a single drive motor is utilized in order to perform indexing (angular rotation of the turret tooling plate) as well as to drive the live tooling. A plurality of live tools can be simultaneously mounted on the turret tooling plate and the single drive motor is selectively engageable with each of the live tools so that only one of the plurality of live tools is driven at a given time. The selective live tool drive train includes an axially movable drive shaft and bevel drive gear for selectively engaging the driven bevel gear of the desired live tool. The axially movable shaft assembly includes a mechanism for adjusting the backlash between the driving and driven bevel gears when these gears are engaged with one another. The turret assembly further includes a clutch for selectively engaging the single drive motor to index the turret tooling plate and an encoder mechanism activated during the indexing operation in order to allow precise tracking of the turret tooling plate during the rotation thereof. A torque limiter is provided in the indexing drive train to disengage the indexing drive in the event of a torque overload occurring during indexing, such as may occur if the turret tooling plate or a tool mounted thereon strikes another object (workpiece, other turret, etc.). The drive motor is variable speed and reversible in order to allow bi-directional indexing following the shortest path and further allowing the live tooling to be bi-directionally driven at variable speeds.
It is therefore an object of the present invention to provide an indexable turret assembly capable of supporting stationary as well as live tooling.
It is also an object of the present invention to provide a turret assembly having an indexable turret tooling plate capable of supporting live tooling and having a single drive unit responsible for driving the live tooling as well as for causing angular displacement of the turret tooling plate during indexing.
It is another object of the present invention to provide a turret assembly having a live tool drive train that is engageable to selectively drive only a single one of a plurality of live tools mounted on the turret tooling plate.
It is another object of the present invention to provide a turret assembly having a selective live tool drive train that includes an axially movable drive shaft and bevel drive gear for selectively engaging the driven bevel gear of the desired live tool and wherein the axially movable shaft assembly includes a mechanism for adjusting the backlash between the driving and driven bevel gears when these gears are engaged with one another.
It is another object of the present invention to provide a turret assembly that includes a clutch for selectively engaging the single drive motor to index the turret tooling plate.
It is another object of the present invention to provide a turret which includes a torque limiter in the indexing drive train to disengage the indexing drive in the event of a torque overload occurring during indexing, such as may occur if the turret tooling plate or a tool mounted thereon strikes another object.
It is another object of the present invention to provide an indexable turret assembly including a variable speed reversible motor drive unit allowing bi-directional indexing following the shortest path and further including reversible bi-directionally driven live tooling.
It is another object of the present invention to provide a turret assembly having an indexable turret tooling plate and encoder mechanism for accurately tracking angular displacement of the turret tooling plate during indexing thereof.